August 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 39456] GRB 250815A: Fermi GBM Final Localization
by GCN Circulars 15 Aug '25

15 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41395 SUBJECT: GRB 250815A: Fermi GBM Final Localization DATE: 25/08/15 15:51:47 GMT FROM: Utkarsh Pathak at IIT Bombay <utkarshpathak.07(a)gmail.com> The Fermi GBM team reports the detection of a likely SHORT GRB "At 11:49:10.84 UT on 15 August 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250815A (trigger 776951355/250815492). The duration and the spectrum suggest an SGR flare, but it is not near the galactic plane, so further follow-up is encouraged. The on-ground calculated location, using the Fermi GBM trigger data, is RA = 221.57, Dec = -1.10 (J2000 degrees, equivalent to J2000 14h 46m, -1d 6'), with a statistical uncertainty of 7.79 degrees. The angle from the Fermi LAT boresight is 30 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250815492/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250815492/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250815492/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/41395. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39455] GRB 250813B: Liverpool Telescope optical upper limits
by GCN Circulars 15 Aug '25

15 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41394 SUBJECT: GRB 250813B: Liverpool Telescope optical upper limits DATE: 25/08/15 14:54:03 GMT FROM: Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515(a)gmail.com> A. Kumar, J. R. Maund (RHUL), N. C. Sun (UCAS), W. X. Li, Y. N. Wang (NAOC), and K. Wiersema (Herts) report: Using the IO:O imager on the 2.0 m Liverpool Telescope, we observed the field of the SVOM/ECLAIRs–triggered GRB 250813B (Xie et al., GCNs 41352, 41354), also detected by EP–FXT (Wu et al., GCN 41361), SVOM/MXT (Götz et al., GCN 41368), Fermi/GBM (Smith et al., GCN 41376), and SVOM/GRM (Tan et al., GCN 41383). Observations in the r and z bands were obtained on 2025-08-15 at 02:42:32.1 UT and 03:13:37.8 UT, corresponding to ~1.16 and ~1.18 days post-trigger, respectively. Each band consisted of 3 × 600 s exposures. We do not detect the optical afterglow of GRB 250813B (Jelinek et al., GCN 41355; de Ugarte Postigo et al., GCN 41356; Schneider et al., GCN 41363; Xin et al., GCN 41369; Corcoran et al., GCN 41370) down to limiting magnitudes of r >22.0 and z >20.6. Photometric calibration was performed using Pan-STARRS stars. The quoted magnitudes are not corrected for Galactic extinction in the direction of the GRB. View this GCN Circular online at https://gcn.nasa.gov/circulars/41394. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39454] GRB 250814A: Further COLIBRÍ optical upper limit
by GCN Circulars 15 Aug '25

15 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41393 SUBJECT: GRB 250814A: Further COLIBRÍ optical upper limit DATE: 25/08/15 14:48:30 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Enrique Moreno Méndez (UNAM), Francesco Magnani (CPPM), Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Fredd Sánchez Álvarez (UNAM), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the Fermi and Swift GRB 250814A (Fermi team, GCN Circ. 41357, Caputo et al. GCN Circ. 41358) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-08-15 03:20 to 04:48 UTC (from 19.8 to 21.2 hours after the trigger) and obtained 64 minutes of exposure in the r filter. The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the XRT source position (Caputo et al. GCN Circ. 41358) or possible optical and infrared counterpart position (Karambelkar et al. GCN Circ. 41377; Castro-Tirado et al., GCN Circ. 41381; Ahumada et al. GCN Circ. 41382; D'Avanzo et al. GCB Circ. 41391; Kumar et al. GCN Circ. 41392) down to the following 3-sigma limit: r > 23.6 We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/41393. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39453] GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
by GCN Circulars 15 Aug '25

15 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41392 SUBJECT: GRB 250814A: detection of the afterglow candidate with Liverpool Telescope DATE: 25/08/15 13:59:44 GMT FROM: Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515(a)gmail.com> A. Kumar, J. R. Maund (RHUL), N. C. Sun (UCAS), W. X. Li, Y. N. Wang (NAOC), and K. Wiersema (Herts) report: We observed the field of the Fermi/GBM and Swift/BAT GRB 250814A (Fermi GBM Team, GCN 41357; Caputo et al., GCN 41358), which is spatially coincident with the sub-threshold GW trigger S250814bg (LVK, GCN 41364), using the IO:O imager on the 2.0m Liverpool Telescope. Multi-band (B, g, V, r, i, and z bands) imaging was obtained between 2025-08-14 23:34:48.3 UT and 2025-08-15 01:29:02.2 UT (corresponding to ~15.99 and 17.90 hours post-trigger, respectively). Based on our preliminary analysis, we detect the counterpart candidate in our stacked z-band image obtained ~16.86 hours post-trigger at RA = 20:25:13.8 and Dec = +48:23:56.5 (J2000), within the Swift-XRT localisation region (Salvaggio et al., GCN 41379); see also Karambelkar et al. (GCN 41377), Castro-Tirado et al. (GCN 41381), Ahumada et al. (GCN 41382) and Source 1 of D'Avanzo et al. (GCN 41391). No source is detected at this position in the B, g, V, r, and i bands. A summary of our observations and preliminary photometric results is provided below. T_obs (start time) T_obs - T0 Exp Filter Mag -------------------------------------------------------------------------------------------- 2025-08-15T00:26:48.9 16.86 2x600 s z 21.3 ± 0.3 2025-08-14T23:34:48.3 15.99 600 s g >21.9 2025-08-14T23:45:18.2 16.16 2x600 s r >22.1 2025-08-15T00:06:03.3 16.51 2x600 s i >21.8 2025-08-15T00:47:35.3 17.21 2x600 s V >22.2 2025-08-15T01:08:24.4 17.55 3x600 s B >20.5 Photometric calibration was performed using stars from the Pan-STARRS (for g, r, i and z bands), USNO-B1 (for B band), and APASS (for V band) catalogues. The quoted magnitudes are not corrected for Galactic extinction in the direction of the GRB. This circular may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/41392. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39452] GRB 250814A: GRAWITA TNG NIR observations
by GCN Circulars 15 Aug '25

15 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41391 SUBJECT: GRB 250814A: GRAWITA TNG NIR observations DATE: 25/08/15 12:07:02 GMT FROM: Paolo D'Avanzo at INAF - OAB <paolo.davanzo(a)inaf.it> P. D'Avanzo, (INAF-OAB), M.T. Botticella, L. Izzo (INAF - OACn), A. Rossi (INAF-OAS), V. D’Elia (ASI-SSDC), G. Greco (INFN), M.G. Bernardini (INAF-OAB), B. Patricelli (Univ. Pisa), E. Cappellaro (INAF-OAPd), E. Brocato (INAF-OAR), V. Lorenzi, G Mainella (INAF-TNG), on behalf of GRAWITA report: We observed the field of GRB 250814A detected by Swift/BAT and Fermi/GBM (Caputo et al. GCN Circ. 41358; Fermi team, GCN Circ. 41357) and possibly associated with the sub-threshold GW trigger S250814bg (LVK, GCN Circ. 41364) with the Italian 3.6m TNG telescope, located in Canary Islands (Spain), equipped with the near-infrared camera NICS in imaging mode. A series of images were obtained with the H filter starting on 2025-08-14T20:33:39 UT (i.e. 13.0 hours post T0) and with the K filter starting on 2025-08-14T22:06:25 UT (i.e. 14.5 hours post T0), centered at the position of the X-ray afterglow detected by Swift/XRT (Caputo et al. GCN Circ. 41358; Salvaggio et al., GCN Circ. 41379). Within the Swift/XRT error circle (Salvaggio et al., GCN Circ. 41379) we detect two sources. Below we report the source positions and AB magnitudes derived from preliminary photometry (calibrated against the 2MASS catalogue). Source 1 RA (J2000) = 20:25:13.86 Dec (J2000) = +48:23:56.3 +/- 0.3" H = 21.3 +/- 0.2 mag K = 21.4 +/- 0.3 mag Source 2 RA (J2000) = 20:25:14.06 Dec (J2000) = +48:23:54.8 +/- 0.3" H = 21.8 +/- 0.2 mag K = 21.2 +/- 0.2 mag We note that Source 1 is the same reported by several authors in both the NIR and optical bands (Karambelkar et al. GCN Circ. 41337; Castro-Tirado et al. GCN Circ. 41381; Ahumada et al. GCN Circ. 41382). Compared with the results reported so far, our preliminary photometry suggests that this source has not varied, in agreement with the findings of Ahumada et al. (GCN Circ. 41382). Further NIR observations are encouraged to check for any brightness evolution of Source 2. View this GCN Circular online at https://gcn.nasa.gov/circulars/41391. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39451] GRB 250812A: SVOM/VT optical continued observation
by GCN Circulars 15 Aug '25

15 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41390 SUBJECT: GRB 250812A: SVOM/VT optical continued observation DATE: 25/08/15 10:57:59 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, Z. H. Yao, L. P. Xin, Y. L. Qiu, C. Wu, H. L. Li, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), Z. M. Wang (BNU) report on behalf of the SVOM/VT team. SVOM/VT conducted continued observations of GRB 250812A detected by SVOM/ECLAIRs（Xin et al., GCN 41322). The magnitudes of the optical afterglow (He et al., GCN 41324; Xin et al., GCN 41326; Rakotondrainibe et al., GCN 41328; Freeberg et al., GCN 41331; Siegel et al., GCN 41344; Santos et al., GCN 41346; van Dalen et al., GCN 41347; de Ugarte Postigo et al., GCN 41348) are: mid time (h) | exposure time (s) | band | mag (AB) | mag err -------------|-------------------|-- ---|----------|-------- 66.572 | 20*70 | VT_R | 21.25 | 0.07 66.572 | 20*70 | VT_B | 21.81 | 0.09 Our photometry was not corrected for Galactic extinction. The optical afterglow initially rises with a temporal slope of 0.5, reaching its peak at approximately 18 hours, followed by a rapid decay with a slope of -2.0. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/41390. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39450] GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
by GCN Circulars 15 Aug '25

15 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41389 SUBJECT: GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg DATE: 25/08/15 10:55:07 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN: We observed the field of GRB 250814A detected by Fermi/GBM (The Fermi GBM team, GCN 41357), Swift/BAT (Caputo et. al, GCN 41358), which was temporally and spatially coincident with a GW event S250814bg detected by LVK (GCN 41364). The observations were carried out with the 1.5m AZT-33IK telescope of the Solar Sayan Observatory (Mondy). The series of 30x120 s images were captured in the R-filter starting on 2025-08-14 at 17:49 UT, i.e. ~0.44 days after the GBM trigger. In the co-add image of 28x120 s we do not detect any optical source at the position of the IR candidate (Karambelkar et. al, GCN 41377; Castro-Tirado et. al, GCN 41381; Ahumada et. al, GCN 41382). The preliminary upper limit on a candidate optical counterpart in the co-add image is presented below: Date UT start t-T0 Exp. Filter OT Err UL (mid, days) (n x s) (3sigma) 2025-08-14 17:51:08 0.44721 28x120 R n/d n/d 22.7 The photometry was calibrated using nearby stars from the PS1 DR2 catalog (R mags were obtained via Lupton 2005 transformations) and not corrected for the Galactic extinction. The candidate counterpart position was also observed in the optical and IR bands by (Becerra et. al, GCN 41362; de Ugarte Postigo et. al, GCN 41367; Karambelkar et.al, GCN 41372; Salazar Manzano et. al, GCN 41375; Jiang et. al, GCN 41387), which resulted in upper limits. View this GCN Circular online at https://gcn.nasa.gov/circulars/41389. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39449] GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
by GCN Circulars 15 Aug '25

15 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41388 SUBJECT: GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit DATE: 25/08/15 10:13:58 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy <giovannicalapai(a)tiscali.it> Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We imaged the field of GRB 250813B detected by SVOM/ECLAIRs telescope (Xie et al. GCN 41352 - 41354), with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-08-14 00:02 UT (approximately 1.19 hours after burst) stacking a set of unfiltered CCD image. The observations were carried out with partially clear skies and Moon (illumination: 74%, distance: 42°). We co-added 93 exposures of 60 sec each. Start T0+ End T0+ CR lim 1.19 hour 4.44 hour 20.1 We did not found any optical counterpart in the error box of the XRTcandidate (Page et al. GCN 41359). Magnitudes were estimated with the PanSTARRS cat. and are not corrected for galactic dust extinction. Our observations are consistent with other already reported Jelinek et al. (GCN 41355), Gill et al. (GCN 41356), Corcoran et al. (GCN 41370). The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/41388. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39448] GRB250814A: TRT optical upper limits
by GCN Circulars 15 Aug '25

15 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41387 SUBJECT: GRB250814A: TRT optical upper limits DATE: 25/08/15 09:39:01 GMT FROM: sqjiang at NAOC <sqjiang(a)bao.ac.cn> S.Q. Jiang (NAOC), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), L.B. He, J. An, X. Liu, Z.P. Zhu, D. Xu (NAOC), S. Y. Fu (HUST) report on behalf of a large collaboration: We observed the field of GRB 250814A detected by Swift (Caputo et al., GCN 41358) and Fermi (Fermi GBM team, GCN 41357), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Sierra Remote Observatories in California. We obtained several 180 s frames in the R and I filters. The observation started at 07:44:15.35 UTC on 2025-08-14, i.e., 9.27 mins after the Swift/BAT trigger time. No new optical source is detected within the Swift/XRT enhanced error circle (Caputo et al., GCN 41358) down to R > 20.7 and I > 19.7 at about 17.3 mins post-burst, calibrated with nearby Pan-STARRS DR2 stars and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/41387. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39447] GRB 250814B: SVOM/GRM observation
by GCN Circulars 15 Aug '25

15 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41386 SUBJECT: GRB 250814B: SVOM/GRM observation DATE: 25/08/15 09:29:26 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Hui Yang (IRAP), Stéphane Schanne (CEA) Report on behalf of the SVOM team: SVOM/GRM was triggered on-ground by GRB 250814B at 2025-08-14T10:22:10.500 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #41366). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 9.0 +2.0/-3.0 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250814B.png The SVOM/GRM on-ground localization of this burst is (J2000): RA: 73.9 deg DEC: 22.2 deg Error: 7.1 deg (1sigma, statistical only) We caution that the calibration of SVOM/GRM is undergoing and this localization is subject to systematic errors. The SVOM/GRM on-ground localization is consistent with Fermi/GBM (Fermi GBM Team, GCN #41366) In addition, the position of this burst, as determined by SVOM/GRM, is located at about 71 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view, and is consistent with no indication for subthreshold targets either from CRT and IMT of ECLAIRs. With this localization, the time-averaged spectrum from T0-5 to T0+7 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.46 +0.16/-0.22 and the cutoff energy, parameterized as Epeak, is 250 +395/-91 keV. The event fluence (10-1000 keV) in this time interval is (2.99 +0.43/-0.41)E-06 erg/cm^2. Thus GRB 250814B is consistent with Type II GRBs in the 'Amati' relation diagram, as shown at: https://www.bursthub.cn//admin/static/grb250814B_amati.png The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/41386. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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